For a common slide door opening and closing device, an upper rail, a lower rail and a center rail are attached to an upper part, a lower part and a rear-center part of an entrance opening at a vehicle side face, respectively. To make a slide door opening and closing operation, rollers, rotatabily supported to brackets fixed to the slide door, are slid along each rail.
In an automatic opening and closing device for a vehicle slide door, a belt driving system, a wire driving system, a cable driving system or others is commonly applied with being assembled on vehicle step panel which is used as an entrance step for getting on or off of passenger.
An example of a belt driving system has been disclosed in a Japanese Patent Laid-Open Publication published as No. Hei. 10(1998)-8828. In the disclosed belt driving system, a motor, a driving pulley driven by the motor, a driven pulley (provided at both fore side and rear side of a step panel), and an idle pulley are displaced on the under surface of the step panel and assembled as a belt driving system module. The step panel is attached on the vehicle body with a space under it for accommodating the belt driving system mechanism therebetween. A loop-like timing belt extends fore and aft and is wound on each pulley, and a part of a slide door is fixed to the timing belt through a bracket. Then, the slide door can move to open or close.
In this system, an output rotation axis of a drive motor points to vertical direction because of the relationship between the driving pulley and the timing belt. In this configuration, projected area on a horizontal plane of the drive motor is wider than projected area on a vertical plane, because the drive motor usually is attached with drive mechanisms including such as a magnetic clutch. In actual design, a part of the step panel has to be deformed to inflate upward to ensure the height space for accommodating the drive motor. Therefore, the wider the infrared area of the step panel for the space to the drive motor becomes, the narrower the entrance step area for the passenger is. Therefore, design flexibility of the step panel is restricted, and ease in getting on and off becomes worse.
For a wire or a cable driving system, Japanese Patent Laid-Open Publications published as Nos. Hei. 8(1996)-232539 and Hei. 5(1993)-61432 have been disclosed. In these systems, a driving pulley driven by a motor and a driven pulley (provided at both fore side and rear side of a step panel) are provided under the step panel of a vehicle. In addition, a loop-like wire (or cable) is wound on each pulley, and a part of a slide door is fixed to a one end of the wire. Then, the slide door can move to open or close.
These wire or a cable driving system have design flexibility for the arrangement of an output rotation axis of a drive motor points in vertical or horizontal direction. However, an effective length of the wire is considerably changed, when a lower roller of the slide door is moving at either a straight line path or a curved line path of a rail. Then, a tension adjusting pulley is required to provide on the path of the wire. It makes the structure complex and makes the number of parts increase. In the structure of a cable driving system disclosed in Japanese Patent Laid-Open Publication published as No. Hei. 8(1996)-232539, durability of the cable may be worse, because sliding operation between the cable and a guiding tube may cause wearing.
These difficulties can not be eliminated even if the belt is simply alternated to a wire or a cable for the belt driving system described previously. More specifically, even if the belt is simply alternated to a wire, the conversion of the output rotation axis direction of the driving motor and the change of the effective length of the wire can not be eliminated all together.